As highlighted in the Surgeon General's Call to Action to Prevent Suicide (1999), effective suicide prevention strategies are sorely needed. Despite substantial knowledge about adolescent suicide risk factors, there is a paucity of research on effective interventions. Few randomized controlled intervention trials have been conducted with suicidal adolescents, and treatment adherence among these adolescents is generally poor. This randomized controlled trial will investigate the efficacy of the Youth-Nominated Support Team Intervention (YST), a psychoeducational, social network intervention that targets two problems common among suicidal adolescents, poor treatment adherence and negative perceptions of family and social support. It targets these problems during a period of high risk for suicidal behavior, the 12-month period following psychiatric hospitalization. Suicidal adolescents (n = 532) will be recruited from the Child and Adolescent Psychiatric Hospital at the University of Michigan and Havenwyck Hospital, a large private psychiatric hospital. Adolescents will be randomly assigned to either treatment-as-usual (TAU) or treatment-as-usual plus YST (TAU+YST). Adolescents assigned to TAU+YST will nominate three or four adults from family, school, and community settings to function as support persons. Nominated support persons participate in a psychoeducation session that focuses on the adolescent's psychiatric disorder(s), individualized treatment plan, importance of treatment adherence, and suicide risk factors. During the 3-month YST intervention, support persons maintain regular contact with the adolescent to support treatment adherence and progress toward treatment goals. The YST intervention specialist maintains regular telephone contact with each support person to provide information and address concerns. Adolescents will be contacted for 6-week, 3-month, 6-month, and 12-month assessments. The efficacy of YST will be measured by reductions in (a) severity and frequency of suicidal ideation, (b) severity of depression and anxiety, (c) suicide attempts, (d) internalizing behavior problems, and by improvements in (e) perceived social support, (f) treatment adherence, and (g) adaptive functioning. Repeated measures analyses will test overall intervention effects, the hypothesized moderating effect of gender, and the extent to which intervention effects are maintained. Results of this study are expected to provide information about the effectiveness of YST for suicidal adolescents, addressing a critical gap in our understanding of strategies for improving treatment adherence and reducing suicide risk among these adolescents.